From: "Bryan J. Smith" <b.j.smith@ieee.org>
To: Justin Piszcz <jpiszcz@lucidpixels.com>,
Bryan J Smith <b.j.smith@ieee.org>
Cc: xfs-bounce@oss.sgi.com, Ralf Gross <Ralf-Lists@ralfgross.de>,
linux-xfs@oss.sgi.com, linux-raid@vger.kernel.org
Subject: Re: mkfs options for a 16x hw raid5 and xfs (mostly large files)
Date: Wed, 26 Sep 2007 10:11:56 -0700 (PDT) [thread overview]
Message-ID: <673292.62672.qm@web32906.mail.mud.yahoo.com> (raw)
In-Reply-To: <Pine.LNX.4.64.0709261223290.15219@p34.internal.lan>
Justin Piszcz <jpiszcz@lucidpixels.com> wrote:
> I have a question, when I use multiple writer threads (2 or 3) I
> see 550-600 MiB/s write speed (vmstat) but when using only 1
thread,
> ~420-430 MiB/s...
It's called scheduling buffer flushes, as well as the buffering
itself.
> Also without tweaking, SW RAID is very slow (180-200
> MiB/s) using the same disks.
But how much of that tweaking is actually just buffering?
That's a continued theme (and issue).
Unless you can force completely synchronous writes, you honestly
don't know. Using a larger size than memory is not anywhere near the
same.
Plus it makes software RAID utterly n/a in comparison to hardware
RAID, where the driver is waiting until the commit to actual NVRAM or
disc is complete.
--
Bryan J. Smith Professional, Technical Annoyance
b.j.smith@ieee.org http://thebs413.blogspot.com
--------------------------------------------------
Fission Power: An Inconvenient Solution
prev parent reply other threads:[~2007-09-26 17:11 UTC|newest]
Thread overview: 48+ messages / expand[flat|nested] mbox.gz Atom feed top
2007-09-23 9:38 mkfs options for a 16x hw raid5 and xfs (mostly large files) Ralf Gross
2007-09-23 12:56 ` Peter Grandi
2007-09-26 14:54 ` Ralf Gross
2007-09-26 16:27 ` [UNSURE] " Justin Piszcz
2007-09-26 16:54 ` Ralf Gross
2007-09-26 16:59 ` Justin Piszcz
2007-09-26 17:38 ` Bryan J. Smith
2007-09-26 17:41 ` Justin Piszcz
2007-09-26 17:55 ` Bryan J. Smith
2007-09-26 17:13 ` [UNSURE] " Bryan J. Smith
2007-09-26 17:27 ` Justin Piszcz
2007-09-26 17:35 ` Bryan J. Smith
2007-09-26 17:37 ` Justin Piszcz
2007-09-26 17:38 ` Justin Piszcz
2007-09-26 17:49 ` Bryan J. Smith
2007-09-27 15:22 ` Ralf Gross
2007-09-24 17:31 ` Ralf Gross
2007-09-24 18:01 ` Justin Piszcz
2007-09-24 20:39 ` Ralf Gross
2007-09-24 20:43 ` Justin Piszcz
2007-09-24 21:33 ` Ralf Gross
2007-09-24 21:36 ` Justin Piszcz
2007-09-24 21:52 ` Ralf Gross
2007-09-25 12:35 ` Ralf Gross
2007-09-25 12:50 ` Justin Piszcz
2007-09-25 13:44 ` Bryan J Smith
2007-09-25 12:57 ` KELEMEN Peter
2007-09-25 13:49 ` Ralf Gross
2007-09-25 14:08 ` Bryan J Smith
2007-09-25 16:07 ` Ralf Gross
2007-09-25 16:28 ` Bryan J. Smith
2007-09-25 17:25 ` Ralf Gross
2007-09-25 17:41 ` Bryan J. Smith
2007-09-25 19:13 ` Ralf Gross
2007-09-25 20:23 ` Bryan J. Smith
2007-09-25 16:48 ` Justin Piszcz
2007-09-25 18:00 ` Bryan J. Smith
2007-09-25 18:33 ` Ralf Gross
2007-09-25 23:38 ` Justin Piszcz
2007-09-26 8:23 ` Ralf Gross
2007-09-26 8:42 ` Justin Piszcz
2007-09-26 8:49 ` Ralf Gross
2007-09-26 9:52 ` Justin Piszcz
2007-09-26 15:03 ` Bryan J Smith
2007-09-26 15:15 ` Ralf Gross
2007-09-26 17:08 ` Bryan J. Smith
2007-09-26 16:24 ` Justin Piszcz
2007-09-26 17:11 ` Bryan J. Smith [this message]
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